This invention generally relates to mechanical connections for general purposes and more specifically to locks and joints for telescopically coupled tubes.
It is often desirable to lock telescopic tubes together and be able to vary their overall end-to-end length. Many conventional mechanical fasteners can accomplish this.
One particular type of fastener can lock telescopic tubes together with wedging or camming force as the tubes are twisted relative to one another in either direction. Telescopic joints or connections of this type are disclosed in U.S. Pat. 2,473,351 to Thompson et al. (1949) and U.S. Pat. No. 2,517,700 to Odin (1950).
A basic component incorporated in these fasteners is an eccentric pin fixed to one tube with its axis off-set from the axis of the same tube. Rotation forces the eccentric pin to engage and wedge against a lock ring in order to accomplish locking. Rotation in the opposite direction accomplishes unlocking so the overall tube length can be selectively adjusted.
A problem with this particular type of fastener is that when conventional telescopic tubes are employed, the lock ring tends to slip and spin around under the lateral thrust exerted by the eccentric pin.
Another problem is caused by the fact that the locking action can be accomplished by twisting the tubes either clockwise or counter-clockwise. Therefore, when the same or a different person attempts to unlock the telescopic joint and mistakenly twists the tubes in the wrong direction, i.e., the locking direction, severe jamming occurs. Excessive torque exerted in the wrong direction can eventually rupture the components of the joint, the tubes or a handle if provided.
This invention is primarily aimed at overcoming these problems associated with conventional locks or joints for telescopic tubes.